Context and Data Flow Diagrams Activity presented by Coral Shand March 2012 Scenario The Car Club has many enthusiastic members. Prospective members can join the club by sending in a membership form along with $10. A planning committee decides on new activities for the coming month and these are passed on to members in a monthly newsletter. Information about all activities past and present are stored for future use. Members also receive reminder letters when their membership is due for renewal. CONTEXT DIAGRAM Prospective Member The Car Club Member Planning Committee Information in the scenario Name the data flows Membership form Planned activities Monthly newsletter Membership renewal New member details Planned activities Newsletter Renewal reminder External Entity Prospective member Data flow IN (into the system) • New member details • Newsletter • Renewal reminder Member Planning committee Data flow OUT (out of the system) • Planned activities CONTEXT DIAGRAM Prospective Member The Car Club Newsletter Member Planning Committee New member details Renewal Reminder Planned activities Data flow arrows in Context Diagram New member details Newsletter Renewal Reminder Planned Activities Processes for Data Flow Diagram Add new member Add planned activities Create newsletter Create renewal reminder DATA FLOW DIAGRAM Prospective Member Create newsletter Add new member Create renewal reminder Member Add planned activities Planning Committee Members Activities Prospective Member DATA FLOW DIAGRAM Create newsletter Add new member Activities Members Create renewal reminder Member Add planned activities Planning Committee Prospective Member DATA FLOW DIAGRAM New member details Create newsletter Add new member Member details Activities Members Create renewal reminder Renewal reminder Member Member details Add planned activities Planning Committee DATA FLOW DIAGRAM Prospective Member Member details New member details Create newsletter Updated activities Add new member Updated activities Member details Activities Members Create renewal reminder Renewal reminder Member Add planned activities Member details Newsletter Planned activities Planning Committee TEN RULES 1. 2. 3. 4. An external entity must be an intelligence. Data flows are labelled with adjective-noun. Processes are named with a verb-noun. A data flow arrow coming from a process cannot have the same name as a data flow arrow going into that process. 5. Processes and data stores must have at least one data flow arrow in and one out. 6. A data store cannot link directly to another data store. An external entity cannot link directly to another external entity. 7. Data flows from external entity may keep the same name. Data flowing to and from a data store must have the same name. 8. Events at same time are one event. 9. Data flow arrows should not cross each other. 10. Do not use words ‘data’ or ‘process’ in label names.